1. Field of the Invention
The invention relates to a power supply for electronic data processing equipment, and more particularly, to a secure power supply for electronic data processing equipment.
2. Description of the Related Art
Electronic computers increasingly play a central role in many aspects of modern life, both in homes and businesses. These computers range in size from large mainframes which process enormous amounts of data to ubiquitous personal computers such as International Business Machines (IBM) compatible personal computers. These electronic computers require electrical power from an alternating current (AC) power outlet or line. Unlike most appliances and machines powered by electricity where improper shutdowns do not result in any permanent loss or damage to the machine, electronic computers behave poorly when confronted with sudden and unexpected power losses.
In a typical computer operation, data files in a disk drive are opened before they are accessed and retrieved into the computer's memory. The data is processed by a central processing unit, and the results are written back to the memory or the disk drive. The data files contain data or operating instructions which are subject to being lost if power is removed from the computer system without first closing the data files.
In the computer, instructions and data in the form of key strokes may also be entered into the computer through a keyboard. If the data or key strokes should become lost during the power loss, or if there is some alteration of the software operating environment as a result of the power loss, it may be difficult or impossible to recover or reconstruct the information later. For instance, if the removal of power occurs during the installation of the operating system or the formatting of the disk drive, the system will be rendered inoperative. Further, certain alterations caused by improper shutdowns are quite subtle in nature and result in more serious problems because the computer user may obtain erroneous results without warnings and clues as to their cause.
In addition to accidental shutdowns caused by authorized personnel, computer equipment also face the risk of malicious shutdowns by unauthorized personnel. For example, a malevolent individual can shut down the computer equipment without notifying the proper controlling authorities. The malevolent individual can also move or remove the computer equipment without notifying the proper controlling authorities after shutting down the equipment. These malevolent acts could deprive the proper owner of the computer assets and the use of such computer assets. Due to the potential for network server computers to be powered off accidentally or maliciously, it is important that power be removed and the system be shutdown only after proper verification.
The need for controlling the powerdown of the computer system becomes even more paramount in computers with advanced operating systems such as Windows 95.TM. and Windows NT.TM., available from Microsoft Corp. located in Redmond, Wash. These operating systems require the user to shut down the operating system via specific software steps rather than simply turning off the power switch. For example, in Windows 95.TM., the user should click a Start button and select the Shut Down item from the Start menu. The selection of the Shut Down item causes a dialog box to appear on the screen, giving the user the options of shutting down completely, restarting the PC, or exiting to the disk operating system (DOS).
In these advanced operating systems, the shutdown procedure is needed because numerous pieces of status information and configuration data residing in a Windows registry file are not updated until the system has been properly shutdown. Further, data stored in the disk cache are not flushed to disk until the user properly exits Windows 95.TM. or Windows NT.TM.. Thus, the removal of power without following the proper shutdown procedure can corrupt the Windows registry file and compromise the overall reliability of the computer during subsequent operations.
Personal computers also constitute important tools at home for entertainment, education, or work-related purposes. However, in the home environment, children can accidentally turn off power to the system because they don't realize the significance of toggling the power supply on/off switch. Further, non-technical users may accidentally turn off their computers before they have properly saved their work. Although the results of unintentional shutdowns are not as drastic or severe as those in a business environment, an improper removal of power causes the same problems for home computers. Thus, the removal of power from a home computer system should be taken only after proper authorization to prevent problems caused by accidental or malicious computer shutdowns.